As of 2003, the city has an estimated population of 150,176 and the density of 3,356.64 persons per km². The total area is 44.74 km².
Iruma and neighboring Sayama are famous for the tea they produce. Iruma also has well-known textile and brewery industries.
During the Edo period, Iruma was famous as a market and post-statoin town
Iruma Air Base, a facility of the Air Self Defence Force, takes its name from this city. It is located here and in Sayama. Aircraft based here are YS-11, T-4, and C-1. This air base was once known as Johnson Air Base, under the control of the United States Air Force.